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/*
 * Copyright 2013 Red Hat Inc. and/or its affiliates and other contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,  
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.switchyard.handlers;

import java.util.Arrays;
import java.util.HashSet;

import javax.xml.namespace.QName;

import org.jboss.logging.Logger;
import org.switchyard.BaseHandler;
import org.switchyard.Exchange;
import org.switchyard.ExchangePhase;
import org.switchyard.HandlerException;
import org.switchyard.Property;
import org.switchyard.internal.transform.BaseTransformerRegistry;
import org.switchyard.label.BehaviorLabel;
import org.switchyard.metadata.JavaTypes;
import org.switchyard.metadata.ServiceOperation;
import org.switchyard.runtime.RuntimeMessages;
import org.switchyard.transform.TransformSequence;
import org.switchyard.transform.Transformer;
import org.switchyard.transform.TransformerRegistry;

/**
 * ExchangeHandler implementation used to introduce transformations to the
 * exchange handler chain.  The core runtime automatically creates a
 * TransformHandler and attaches it to the consumer handler chain for every
 * exchange.  TransformHandler can also be used in the service provider's
 * chain by using the TransformHandler(Transformer)
 * constructor.
 *
 */
public class TransformHandler extends BaseHandler {

    private static Logger _logger = Logger.getLogger(TransformHandler.class);

    private TransformerRegistry _registry;

    /**
     * Create a new TransformHandler.  The specified TransformerRegistry will
     * be used to locate transformers for each handled exchange.
     * @param registry transformation registry to use for lookups of transformer
     * instances
     */
    public TransformHandler(TransformerRegistry registry) {
        _registry = registry;
    }

    /**
     * Create a new TransformHandler.  The specified list of transforms will
     * be used in place of a TransformerRegistry to locate transforms for each
     * handled exchange.
     * @param transforms transform map
     */
    public TransformHandler(Transformer ... transforms) {
        if (transforms != null && transforms.length > 0) {
            _registry = new BaseTransformerRegistry(
                    new HashSet>(Arrays.asList(transforms)));
        }
    }

    /**
     * Transform the current message on the exchange.
     * @param exchange exchange
     * @throws HandlerException handler exception
     */
    @Override
    public void handleMessage(Exchange exchange) throws HandlerException {
        // Initialize transform sequence for operation types
        if (exchange.getPhase() == ExchangePhase.IN) {
            initInTransformSequence(exchange);
        } else {
            initOutTransformSequence(exchange);
        }
        
        // Apply transforms to the message...
        TransformSequence transformSequence = _registry.getTransformSequence(TransformSequence.getCurrentMessageType(exchange), TransformSequence.getTargetMessageType(exchange));
        if (transformSequence != null) {
            transformSequence.associateWith(exchange.getMessage());
        }
    
        TransformSequence.applySequence(exchange, _registry);
        if (!TransformSequence.assertTransformsApplied(exchange)) {
            QName actualPayloadType = TransformSequence.getCurrentMessageType(exchange);
            QName expectedPayloadType = TransformSequence.getTargetMessageType(exchange);
            throw RuntimeMessages.MESSAGES.transformationsNotApplied(expectedPayloadType.toString(), 
                    actualPayloadType.toString());
        }

        // Replace the CONTENT_TYPE property to indicate current content type after transform
        setContentType(exchange);
    }

    @Override
    public void handleFault(Exchange exchange) {
        // Apply transforms to the fault...
        initFaultTransformSequence(exchange);
        TransformSequence.applySequence(exchange, _registry);
        if (!TransformSequence.assertTransformsApplied(exchange)) {
            QName actualPayloadType = TransformSequence.getCurrentMessageType(exchange);
            QName expectedPayloadType = TransformSequence.getTargetMessageType(exchange);

            if (_logger.isDebugEnabled()) {
                _logger.debug("Transformations not applied.  Required payload type of '" + expectedPayloadType + "'.  Actual payload type is '" + actualPayloadType + "'.  You must define and register a Transformer to transform between these types.");
            }
        }

        // Replace the CONTENT_TYPE property to indicate current content type after transform
        setContentType(exchange);
    }
    
    private void setContentType(Exchange exchange) {
        QName currentType = TransformSequence.getCurrentMessageType(exchange);
        if (currentType != null) {
            exchange.getContext().setProperty(Exchange.CONTENT_TYPE, currentType).addLabels(BehaviorLabel.TRANSIENT.label());
        } else {
            // make sure no property is used for current scope
            Property p = exchange.getContext().getProperty(Exchange.CONTENT_TYPE);
            if (p != null) {
                exchange.getContext().removeProperty(p);
            }
        }
    }

    private void initInTransformSequence(Exchange exchange) {
        QName exchangeInputType = exchange.getContract().getConsumerOperation().getInputType();
        QName serviceOperationInputType = exchange.getContract().getProviderOperation().getInputType();

        if (exchangeInputType != null && serviceOperationInputType != null) {
            TransformSequence.
                    from(exchangeInputType).
                    to(serviceOperationInputType).
                    associateWith(exchange.getMessage());
        }
    }

    private void initOutTransformSequence(Exchange exchange) {
        QName serviceOperationOutputType = exchange.getContract().getProviderOperation().getOutputType();
        QName exchangeOutputType = exchange.getContract().getConsumerOperation().getOutputType();

        if (serviceOperationOutputType != null && exchangeOutputType != null) {
            TransformSequence.
                    from(serviceOperationOutputType).
                    to(exchangeOutputType).
                    associateWith(exchange.getMessage());
        }
    }
    
    private void initFaultTransformSequence(Exchange exchange) {
        QName exceptionTypeName = null;
        ServiceOperation providerOperation = exchange.getContract().getProviderOperation();
        ServiceOperation consumerOperation = exchange.getContract().getConsumerOperation();
        QName invokerFaultTypeName = consumerOperation.getFaultType();

        if (providerOperation != null) {
            exceptionTypeName = providerOperation.getFaultType();
        }

        Object content = exchange.getMessage().getContent();
        if (exceptionTypeName == null && content instanceof Exception) {
            exceptionTypeName = JavaTypes.toMessageType(content.getClass());
        }

        if (exceptionTypeName != null && invokerFaultTypeName != null) {
            // Set up the type info on the message context so as the exception gets transformed
            // appropriately for the invoker...
            TransformSequence.
                from(exceptionTypeName).
                to(invokerFaultTypeName).
                associateWith(exchange.getMessage());
        }
    }

}